At the Vehicle Testing and Integration Facility (VTIF) in Denver, Colorado, the National Renewable Energy Laboratory is testing sustainable transportation technologies and innovations, including electric vehicle charging and integration into the power grid.

“There are a lot of entities investigating components of electric vehicles, grid integration, or infrastructure,” said NREL Vehicle Systems Engineer Mike Simpson. “There are very few places looking at how they all come together as a much larger, connected system. This facility was designed from the ground up to specifically address that intersection point.”

Capabilities at the VTIF include vehicle energy management within smart grids, vehicle charge integration with renewable energy resources, bi-directional vehicle charge testing and demonstration, and vehicle thermal management. Four test bays at the facility allow for multiple tests to be conducted at once in controlled environments and can accommodate a wide variety of vehicles, including one test bay built specifically to conduct testing on heavy-duty vehicles. An upcoming addition to the facility is an 18-kilowatt solar array, which will be tied directly to vehicle charging and will allow researchers to do expanded work around the use of solar energy to charge electric vehicles within microgrids.

The VTIF has been working on innovations in electric vehicle charging like “fast charging” and “bi-directional charging.”

A four-hour fill up doesn’t quite compete with gasoline engines for on-the-road demand, so engineers are exploring scenarios for fast charging. A fast charge can potentially recharge an electric vehicle in 15 to 25 minutes if the battery is close to empty. This technology employs the conversion of alternating current (AC) grid power to direct current (DC) power, which can be delivered directly to the battery pack. This method allows for faster charges using smaller charging equipment.

Additionally, VTIF researchers are exploring opportunities for bi-directional charging. Bi-directional, or vehicle-to-grid (V2G), charging employs smart charging capabilities but also allows for the vehicle to discharge back to the grid, which turns the vehicle battery into a grid storage device. This capability is of particular interest when combined with microgrids. A microgrid is a potentially self-sufficient segment of the grid that is connected to the power grid at large but has the ability to provide and manage its own energy. In a future scenario where there may be variable production from intermittent renewable sources, readily available storage could buffer that variability. With bi-directional charging, electric vehicles have the potential to play that role, and the vehicle becomes an asset in a smart grid or microgrid. Particular areas of interest for this technology emerge around emergency backup power or the use of vehicle fleets for this purpose.